Control system



7, 1950 R. J. KOCHENBURGER I 2,529,035

CONTROL SYSTEM Filed July 7, 1944 2 Sheets-Sheet 1 Zhwentor ,1950 R. J. KOCHE'NBURGER 2,529,085

CONTROL. SYSTEM Filed July 7, 1944 2 Sheets-Sheet 2 42 42a 42a 50 43d 47 49 48a 3nnentor itomeg Patented Nov. 7, 1 950 CONTROL SYSTEM Ralph J. Kochenburger, Montclair, N. J., assignor to Curtiss-Wright Corporation, a corporation of Delaware Application July 7, 1944, Serial No. 543,832

1 My invention relates to a control system and, more particularly, to a, control system forpreventing over-speeding of a' motor or an engine such, for example, as an aircraft engine.

In accordance with my invention, the speed of an aircraft engine is controlled by changing the pitch of the propeller blades driven by said engine and, in the event that'the fuel supplied to said engine is abruptly and substantiallyincreased, the pitch of the propeller blades is increased-at a rate substantially greater than the normal pitch-change rate.

My invention has reference to a system Wherein pitch change is initiated and'continued in response to abrupt increase in manifold engine pressure or, more or less directly, in response to operation of the throttle, or otherwise as may be desirable. 1

Various other objects, advantages and features of my invention will become apparent from the Q following detailed description.

My invention resides in the control system, control features, arrangements and combinations of an illustration of some of the forms thereof, reference is to be had to the accompanying drawings, in which:

Figure 1 is a diagrammatic view illustrating the invention;

Fig. 2 is a vertical sectional View, partly in elevation, showing a part of my novel'mechanism; and

Fig. 3 is an elevational view illustrating features of the invention.

As shown by Fig. 1, the nose n of an aircraft engine has projecting therefrom a propeller shaft I having secured thereto a hub2comprising'sockets 2a, 2a in which the respective propeller blades 3, 3 are journalled. For pitch-changing, each propeller blade 3 has an integral gear 3a at the shank thereof meshing with a ring gear 4 journalled in the hub 2. The ring gear 4 is driven by a speed-reducing unit, generally indicated at 5, which,'in turn, is driven by a reversible electric motor, schematically shown at 6, and en- 8 Claims. (01. 170'135.72)

invention is applicable to other types of pitchchanging systems. Y Forming apart of the motor 6 are oppositely wound field coils 6a and 6b which provide when energized suitable magnetic fields to cause motor armature rotation for pitch increase or decrease respectively. The field coils 6a and 6b have a common terminal from which a conductor 1 extends to one of a set of brushes la, la coactable with the commutator 6c of the motor 6, the other 'brush !a being connected to a brake coil 8 which, in turn, is connected to the slip ring A. Extending from the field coil 6b is a conductor 9 passing "through a limit stop DP to the slip ring 13. Branching from the field coil 6a are conductors II] and l lwhich extend, respectively, through a limit stop IP toslip ring C and through a limit stop FP to slip ring D. The limit stops DP, IP and F? are normally closed switches which are opened automatically when limiting low, high and feather pitch positions, respectively, of the blades 3 are attained to thereby prevent further operation of their respective pitch-changing circuits until the blades 3 are restored to a pitch range which allows closure of the respective limit switches.

Attached to the brush A is a conductor [2 which is grounded at l3 to comprise a common circuit return. The brush B is connected to the by it automaticallycontrols the motor 6 I v the pitch-changing operation.

closed within a housing 211 suitably secured to branches a'conductor l6 extending to a contact Ila of an automatic governor ll as known'in the art and which, for example, may be of the type disclosedin Patent No. 2,449,452 dated September- 14; 1948;- As hereinafter described, the governor ll has-a normal mode of operation where.-

to effect The-"brush C is connected to the increase pitch terminal of selector switch M by a conductor [8 from which branches a conductor I9 extending to a contact [lb of the governor ll. Attached to the arm of selector switch I4 is a conductor '20 which. is'connected at contact2'l to one terminal of a double-pole double-throw feather switch 22. Y A conductor 23 joins'an arm 22a of switch 22' to one terminal of a battery 24, the other terminal of which is grounded. When the arm 22a of switch 22 is engaged with contact 2 l, the switch 22 is in normal position. 1 j I Leading from the fautomatic terminal of selector switch I 4 is a'conductor 25 which is at closed on a contact 2% connected by a conductor 21 to a central movable contact [7c of the governor ll, the vertical position of which is dependent upon the speed of the aircraft engine.

Extending from the brush D is a conductor 28 which is connected to an arm 22b of feather switch 22 which comprises a contact 29 from which passes a conductor 30 leading to 9, voltage booster V. When the arm 22b of switch 22 is in engagement with contact 29, the switch 22 is in feather position.

Included in the voltage booster V is a motorgenerator unit 3! having a motor armature 3|a, a generator armature 31b and a common field coil 3lc which are operable in connection with a relay 32, the winding of which has its terminal-s connected to conductor 30 and to the generator armature 31b, respectively. When the winding of relay 32 is energized by closure of a load circuit supplied from the conductor 30, the relay contacts are closed with resultant energization of the motor armature 3la and the field coil 3Ic which are connected to the positive terminal of the battery 24 by a conductor 33 and to ground through a conductor 33a and the aforesaid contacts of relay 32. The generator armature 31b upon rotation of the motor armature which drives it, produces a voltage of the sam magnitude as the battery voltage which is added to the battery voltage, thus producing substantially double the normal voltage in the conductor 30. This high voltage is used at times to operate the propeller pitch change motor 6 at high speed to attain a high rate of blade pitch increase for feathering, and for compensating sudden increases in engine Power as will shortly be described. a

Branching from the aforesaid conductor 30 is a conductor 34 which is connected to the armature 260 of the relay 26, said armature 260 being normally open with respect to a contact 26d which is connected to conductor I9 by a conductor 35. The terminals ofthe winding of the relay 26 are connected, respectively, to conductor 25 and to one contact of a power-change anticipator P, a second contact of which is secured to a conductor 3'! which extends to one contact of a pressure-operated switch S, the other contact of which is grounded at 38 by a conductor 39.

.The power-change anticipator P functions, as

. propeller blades. In this manner, manual pitch during most flight conditions. With the relay- 26 in the condition shown, the operation of the arrangement is similar to that of prior art systems.

Whenever a positive voltage is applied to one of the field coils Ba or 6b, current passes through the motor armature windings 6c, brake coil 8, slip ring A, brush A and conductor I2 to ground at I3. When brake coil 8 is thus energized, a mechanical locking arrangement, not shown, is released to permit rotation of motor 6 with resultant increased pitch or decreasedpitch operation of the propeller blades, depending on whether field coil 5a or field coil 61) is energized.

With the switch 22 in normal position, current from the positive terminal of the battery 24 change of the propeller blades can be accomplished at any time desired.

It is to be understood, however, that as the propeller blades reach their limiting increased pitch or decreased pitch positions, the respective limit switches IP or DP will open to prevent further operation of the pitch-changing motor 6 until the blades are returned to their normal pitch range.

With the selector switch [4 in automatic-position, current passes through conductor 25, armature 26a and its normally closed contact 262), and conductor 21 to the central contact 110 of the automatic governor I1. When movable contact llc engages contact l'l b, current flows through conductor I9, brush C", slip rings C and conductor I 0 to the field coil 6a with resultant increase in pitch of the propeller blades. When movable contact. Hc engages contact Ha, current passes through conductor 16, brush B and slip ring B to the field coil 6b with resultant decrease in pitch of the propeller blades. As previously stated, the vertical position ofgthe movable contact llc is dependent upon the speed of rotation of the aircraft engine and the gov ernor l1 accordingly acts, in well understood fashion, to maintain a substantially'constant speed of rotation of the aircraft engine through operation of the described-pitch-changing mechanism.

If the switch 22 is moved to feather position, the circuit to the governor is broken and the Winding of relay 32 is energized by' a. circuit which includes the positive terminal of battery 24, conductor '33, generator armature 31b, the winding of relay 32, conductor 30, contact 29, switch arm 22b, conductor 28', brush D, slip ring D, conductor II, limit stop FP, field gcoil 6a, armature to, brake coil 8; 'slip ring A, brush A and ground connection l3. l '3 Responsive to the' closure of: this circuit, the winding of relay 32 is energized to cause'engagement of its contacts with resultant operation switch S and the relay 26 for temporarily sus- Y pending the operation-pf the-governor H, the

power-change anticipator P being responsive-to is supplied to the arm of selector switch 14 variations in the intake manifold pressure of the aircraft engine, although, ina broader concept, theinvention is not to "be -so limited. Alter natively, the normal mode of operation of' the governor I fl may be modified forthe purposes of the invention. 1 1 U I The power-change vanticipator ,1? comprises va casing 40, Fig-:2, having a flange to whicha tubular nut 4| is secured by a threaded lock nut 42 which cooperates with the aforesaid flange and with suitable washers, as shown. Extending through the nut 4| is a sleeve 43 which is supported therein by a circumferential rib 43a encased in suitable packing 43b which is engaged by a lock nut 44 and an integral flange of the nut 4|. Supported within the sleeve 43 by insulating members 430 and 43d is a rod 45 which, atone end thereof, carriesa suitable contact member 46 and, at the other end thereof, has an enlarged circular contact 41.

Supported by the nut 4| and disposed within the casing 40 is a bellows 48 having an end plate 48a upon which a contact 49 is supported by an insulating strip 49a. As shown, the contact 49 is biased from the contact 41 by a, helical spring 50 which engages said contact 49 and a flange of the sleeve 43. The sleeve 43 is provided further with a contact member 5| which is elect'rically connected with the contact 49 by the sleeve 43 and compression spring 50.

The end plate 48a supports one end of a second bellows 52, the other end thereof being secured to an annular member. 53 which is spaced from a flange 49a of the casing 40 by gaskets 54. Abutting the annular member 53 is a plug 55 which extends within one end of the bellows 52 and has an integral insulating block 55a normally contacting the end plate 48a. The gaskets 54, annular member 53, plug 55 and a cap 56 are all secured to the flange 4911 by screws 4%.

Attached to the plug 55 is a third bellows 51 which is urged to a desired initial position by a helical spring 58 disposed between one end of the plug 55 and a plate 58a secured to one end of said bellows 51. At its outer end, the cap 56 is threaded for the insertion of a tube 59 leading to the manifold of the aircraft engine previously referred to. As shown in Fig. 1, a meter 590. may be utilized to indicate the pressure in the tube 59. Plug 55 is provided with suitable drillings 55a which connect the interior of the bellows 51 with the interior of the bellows 52, these drillings having such size that the air pressure within the aforesaid bellows is always substantially equal while, for a purpose to be described later, the end plate 4-8a is provided with a small vent 48b. When the air pressure within bellows 48 and 52 is substantially equal, the end plate 48a is in such position that contact "49 is not in engagement with contact 41. The plug 55 decreases the effective volume of bellows 52 so as to obtain more complete compression of the air in said bellows 52 and bellows 51.

The operation of the device shown in Fig. 2 is as follows:

When the power output of the aforesaid aircraft engine is increased rapidly, the manifold pressure effective within the chamber E defined by the outer surface of the bellows 51 and the interior surface of the cap 56 is increased rapidly with resultant compression of bellows 51 and the air included therein. Due to the presence of the connecting passages 55a, this increase in pressure is also effective within bellows 52. Accordingly, the air pressure within bellows 52 becomes greater than the air pressure within bellows 48 causing the end plate 48a to move leftwardly against the pressure of spring 50 whereby contact 49 is moved into engagement with contact 41 to thereby form an electrical connection be-.

tween contact 46 and contact 5 I.

Assuming that the manifold pressure, remains substantially constant, air flows slowly from 10817 lows 52 to bellows 48 through the vent 481) until the pressure within the bellows becomes sube stantially equal at which time the force exerted by compression spring will be sufficient to cause rightward motion ofthe end plate 48ato its original position with the result that the 616C:- trical connection between contact 41 and contact 49 is broken. I

Thus, after each rapid increase in manifold pressure there will be a period during WhlChCOIl? tact 41 engages contact 49, in response to the air pressure being greater in bellows 52 than in belw lows 48, this period terminating when the air pressure within bellows 48 and 52 is substantially equalized due to the passage of air through vent 48b. If the manifold pressure increases slowly, there is only -a slight increase in air pressure within bellows 52 and enough air flows into the bellows 48 through the vent 48b to maintain a substantially equal air pressure within the aforesaid bellows with the result that contact 49 does not move leftwardly into engagement with contact 41 If the manifold pressure decreases, bellowsv 51 is extended with resultant decrease in air pressure within bellows 52. In this case the air pres sure within bellows 48 is greater than the air pressure within bellows 52 and the endplate 48a remains in engagement with the stop a with the result that contact 49 remains disengaged from contact 41.

.Thus, the power-change anticipator P operates only in response to a rapid increase in manifold pressure and after each such rapid increase, there is a period during which contact 48 is electricall connected to contact5l. r

As shown, the pressure switch S,;Fig'. 1, is operable in connection with an air speed meter which has tubes 6| and 62 extending therefrom to the pitot line and static line of the aircraft, respectively, these lines being provided on most aircraft for measuring airspeed. Branching from tubes 6| and 62 are tubes 63 and 64, respectively, which extend to the pressure operated switch S. As the construction and operation of pressure switches are well known in the prior art, it is sufficient to state that, at low air speeds, the pressure switch S is open and there is no connection between conductor 31 and conductor 39 while, at flight speeds, anelectrical connection is formed between the aforesaid con ductors 31 and 39.

It was hereinbefore explained that, during normal operation, the switch arm 22a remains permanently in engagement with the contact 2|. It was also explained that movement of I the switch 22 to feather position caused energization of the winding of relay 32 whereby increased voltage was applied to the field coil 6a of the pitchchanging motor.

The relay 26 is controlled solely by the powerchange anticipator P and the pressure switch S; When the latter is operated, conductors 39 and 31 are connected together and, when the power: change anticipator P is operated, the contacts 41 and 49 are engaged. When both of these de'- vices are operated, a circuit exists from ground by way of conductor 39, the closed contacts" of the switch S, conductor 31, the closed contacts 41 and 49 of the power-change anticipator P, the winding of relay 26, conductor 25, the movable army of switch I4, conductor 20, contact 2|, switch arm 22a, conductor 23, battery 24 and thence to g toundi As a result' of"-closure of-thecircuit just described, high voltage, as used for feathering, isapplied to theincreasepitch windingfia of the motor'fi over a; circuit which extends from ground byway ofbattery 24, conductor 33, generator armature 3H),- the winding of relay 32-, conductor conductor 34, armature 250 of relay 26; contact 26d, conductor 35 and thence through-the winding 6a and to ground over the'circuitpreviou sly described for increasing the pitchofthe propeller blades. As will beunderstooch should the contacts ofeither the power-change anticipator P or the switch S be opened, the circuit last described is opened with resultant deenergization of the relay 26. This restores the circuit to its-normal condition so that only normal voltage can be applied to the pitch-changing'motor.

-Preferably, in accordance with the invention, the switch S is so adjusted that-the contacts thereof are incapable of closing when the aircraft is 'moving at a speed lower than'some selected speed, for example," 80 milesper hour. At aircraft speeds above this selected speed, the contacts of switch S remain closed at all times. Accordingly, at aircraft speeds higher than the selected speed, the control of the relay 26 resides solely in the power-anticipator P and' at speeds lower than the selected speed, the-poweranticipator P is-incapable of closing the circuit of the relay 26.

Accordingly, if during flight of the aircraft, the, manifold pressure of the aircraft engine is abruptly andsubstantially increased as occasioned, for'example, by quick, substantial advance of the throttle by the pilot, the power-anticipator P operates in the manner hereinbefore described to close its contacts 41, 49with the result that the relay 26 is energized and the pitch of the propeller blades is abruptly increased at the feathering speed. Such increase in pitch of the propellers continues until (1) the relay 2% is deenergized by separation of the switch contacts 41 and 49, or (2) until said relay 26 is deenergized by separation of the contacts of the switch S, 'or

(3) until the limit switch IP is opened.

As hereinbefore described, the power-change anticipator P is controlled in responseto changes in manifold pressure of the aircraft engine. It shall be understood that the invention is not to be thus limited since the power-change anticipator. P may be operated by other devices which are utilized to control the power output of the aircraft engine.

For an example of the invention as last described, reference is to be had to Fig. 3 wherein the power-change anticipator P is generally similar to the one described above. Extending from 8 blade's at-feather speed in the manner haunts foredescribed. a

Thecontrol system-of Fig. 3' may be-operated 'eitherby pneumatic or hydraulic pressure. If the operation, is'by hydraulic pressure, an accumulator-Hl should be'connected to the tube so that a reservoiris provided for the hydraulic fluid as the pressure transmitted thereby increases. I In viewof all the foregoing, it follows that, by my invention, thepitch' of the propeller blades is quickly increased in response to sudden, 'substantialincreasein manifold pressure of the aircraft engine or in response to a substantial and abrupt change in some other condition affecting the power output of said aircraft engine. This is done by removing the control of the pitchchanging operation from the governor (which may respond too slowly) and immediately trans ferring that control to the power-change anticl pator P which is of the quick-response type and which develops a contact-closing. pressure in its operating chambers proportional to the power which the engine is to developresponsive to the increased amount of fuel supplied thereto. a result, the pitch of the propeller bladesisincreased. preferably at the feather rate hereinbefore described? Therefore; harmful overspeeding of the engineis' prevented. While the invention, has been described with respectto certain particular preferred examples which give satisfactory results, it will be understood by those skilled inthe art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended therefore in the appended claims to cover all suchchanges and modifications.

What is claimed as new and desired to be secured by Letters Patent is: Y r

' 1. In a variable pitch propeller system, an aircraft having an engine, a propeller hub driven thereby, propeller blades journalled in said hub, means for changingthe pitch of said propeller blades, means comprising a control are upon which the pressure varies in accordance with changes in thepower of said engine, means initiating a period of operation of said pitch-changing means only in response to a rapid change in pressure upon said control rea from any initial pressure value to thereby increase the pitch of said propeller blades, means for terminating the operation of said pitch-changing means at the end of said period, and means responsive to, the speed of said aircraft for'preventing the opera.- tion. of: said third-named means when the aircraft is moving at a relatively slow speed during the power-change anticipator, P of Fig. 3Jis a tube-65, which corresponds with the tube 59 of Figs. 1 and 2, said tube 65 leading to a suitably supported bellows 6.6 which is connected by a rod 6:1 to a lever 68 having pivoted thereto a rod 69 leading to a carburetor or control mechanism, not shown, for the power supply of the aircraft engine. Hence, the lever 68-is the throttle lever and, when actuated by the pilot in a counterclockwise direction, Fig. 3, to increase the fuel supply for the engine, the bellows 66 is'automatically compressed with resultant compression of; air therein, in the tube 65 and in the operating chambers of the power-change anticipator P. Asthe result'of such movement of the lever 68, then, the contact 47, 49 are closed and this is accompanied by change in pitch of the propeller to normal. changes in manifold pressure.

3. In a control system, a prime mover, varia ble load therefor havingla. normal rate ofvariation controlled by a governor and having a high rate of variation, a manifold pressure changer for said prime mover, means responsive to sudden and substantial increase in manifold pressure of said prime mover from any initial value, means actuated by said responsive means to terminate governor control, and means also actuated by said responsivce means to increase said variable load at its high rate of load variation, said load increasing and governor terminating means being ineffective to alter said variable load in response to normal changes in manifold pressure, and said load increasing and governor terminating means including mechanism to render it inoperative upon cessation of said sudden and substantial increase in manifold pressure.

4. In a control system in combination, a prime mover, a variable load therefor, a first means for changing s-aid variable load at normal rate and at higher than normal rate, a governor responsive to normal changes in the operating condition of said prime mover for operating said variable load changing means at normal rate, a second means including a circuit operable in response to sudden and substantial power change of said prime mover from any initial power setting, third means operated by said second means to operate said variable load changing means at higher than normal rate in the sense of increasing load with increasing power, and an interrupter in said circuit for rendering said second means inoperative, said interrupter being operated by a device sensitive to variations in another quantity resulting from prime mover operation.

5. In a control system in combination, a prime mover, a variable load therefor, a first means for changing said variable load at normal rate and at higher than normal rate, a governor responsive to normal changes in the operating condition of said prime mover for operating said variable load changing means at normal rate, a second means operable in response to sudden and substantial power change or said prime mover from any initial power setting, a third means operated by said second means to operate said variable load changing means at higher than normal rate in the sense of increasing load with increasing power, and mechanism operated by said third means to temporarily terminate governor control of the normal rate load change, and to restore normal rate load changing to said governor after termination of said sudden power change.

6. In aircraft in combination, a power plant comprising an engine and a variable pitch propeller driven thereby, first means for changing the pitch of the blades of said propeller at a normal rate of change and at a higher than normal rate of change, second means responsive to normal engine operation variations to change propeller blade pitch at said normal rate, a third means including an operating system responsive to abrupt and substantial power change of said engine from any initial power setting to change propeller blade pitch at said higher than normal rate in the sense of increasing load with increasing power, the operating system of said third means including mechanism, upon operation of the means, to interrupt pitch change control at said normal rate, and to restore pitch change to the normal rate Ill upon termination of said substantial and abrupt power change, and an air speed responsive interrupter in said operating system for rendering said third means inoperative when aircraft speed is less than a selected speed.

7. In an aircraft power plant including an engine and a controllable pitch propeller driven thereby, in combination, a power plant speed responsive governor normally operable to maintain speed substantially constant by altering propeller pitch, said governor and propeller at times being so slow in response as to permit engine overspeeding beyond the governed value when abrupt and substantial increase in engine power is effected, a device responsive to abrupt and substantial engine power increase, means to effect propeller pitch increase at higher than governor controlled rate, and means responsive to operation of said device to remove control of said propeller from said governor and to impose control of said propeller on said high rate pitch increasing means to minimize propeller overspeeding.

8. In an aircraft power plant including an engine and a controllable pitch propeller driven thereby, in combination, a power plant speed responsive governor normally operable to maintain speed substantially constant by altering propeller pitch, said governor and propeller at times being so slow in response as to permit engine overspeeding beyond the governed value when abrupt and substantial increase in engine power is effected, a device responsive to abrupt and substantial engine power increase, means to eiTect propeller pitch increase at higher than governor controlled rate, and means responsive to operation of said device to remove control of said propeller from said governor and to impose control of said propeller on said high rate pitch increasing means to 'minimize propeller overspeeding, said latter means being operable to restore propeller pitch control at normal rate to said governor upon termination of said abrupt power increase.

RALPH J. KOCHENBURGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,128,983 Blanchard Sept. 16, 1938 2,187,120 Gosslau, et al Jan. 16, 1940 2,195,036 Palmer Mar. 26, 1940 2,334,967 Thomas, et a1 Nov. 23, 1943 2,346,007 Chillson Apr. 4, 1944 2,346,916 Halford, et al. Apr. 18, 1944 2,391,323 Martin Dec. 18, 1945 2,449,452 Chillson Sept. 14, 1948 FOREIGN PATENTS Number Country Date 538,386 Great Britain July 31, 1941 OTHER REFERENCES Mennesson, A. P. C. application, Serial No. 297,931, published May 18, 1943. 

